Suboptimal compilation of window-scaling pflang from jsnellman #215
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Or is this a failure? The --bpf-lua compilation also appears to reject IPv6 as well. Bizarre. |
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Yeah, this doesn't really match my mental model of IPv6 support at all, but it's certainly present in libpcap too :-) A more reasonable test case, 'ip6 and tcp and (tcp[tcpflags] != 0)'. This seems to be the offending code in libpcap, so seems like you're bug-compatible :-) |
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@jsnell interesting :) Passing |
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(in case it's not clear, the example from my above comment means that libpcap sees the given expression as always false, so it might not be a pflua bug.) |
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...and the reason why 'ip6 and tcp[tcpflags] != 0" doesn't match is because accessing packet data via tcp[] only succeeds if the packet is ipv4. Quoth the "specification": The expression ‘ip[6:2] & 0x1fff = 0’ catches only unfragmented IPv4 datagrams and frag zero of fragmented IPv4 datagrams. This check is implicitly applied to the tcp and udp index operations. For instance, tcp[0] always means the first byte of the TCP header, and never means the first byte of an intervening fragment. |
wingo
changed the title
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Edited title to indicate that what I thought was a correctness bug is actually a "feature" of pflang. Leaving the bug open as a task to eventually compile this expression more optimally. |
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FWIW current compilation looks like this; haven't taken a look yet to figure out what could be better local lshift = require("bit").lshift
local band = require("bit").band
local cast = require("ffi").cast
return function(P,length)
if length < 54 then return false end
if cast("uint16_t*", P+12)[0] ~= 8 then return false end
if P[23] ~= 6 then return false end
if band(cast("uint16_t*", P+20)[0],65311) ~= 0 then return false end
local v1 = lshift(band(P[14],15),2)
if (v1 + 28) > length then return false end
if band(P[(v1 + 27)],2) == 0 then return false end
local v2 = (v1 + 35)
if v2 > length then return false end
local v3 = P[(v1 + 34)]
if v3 == 3 then return true end
if v3 == 1 then goto L19 end
do
if (v1 + 36) > length then return false end
local v4 = P[v2]
local v5 = (v1 + v4)
local v6 = (v5 + 35)
if v6 > length then return false end
local v7 = P[(v5 + 34)]
if v7 == 3 then return true end
if v7 == 1 then goto L29 end
do
if (v5 + 36) > length then return false end
local v8 = (v4 + P[v6])
local v9 = (v1 + v8)
local v10 = (v9 + 35)
if v10 > length then return false end
local v11 = P[(v9 + 34)]
if v11 == 3 then return true end
if v11 == 1 then goto L39 end
do
if (v9 + 36) > length then return false end
local v12 = (v8 + P[v10])
local v13 = (v1 + v12)
local v14 = (v13 + 35)
if v14 > length then return false end
local v15 = P[(v13 + 34)]
if v15 == 3 then return true end
if v15 == 1 then goto L49 end
do
if (v13 + 36) > length then return false end
local v16 = (v12 + P[v14])
local v17 = (v1 + v16)
local v18 = (v17 + 35)
if v18 > length then return false end
local v19 = P[(v17 + 34)]
if v19 == 3 then return true end
if v19 == 1 then goto L59 end
do
if (v17 + 36) > length then return false end
local v20 = (v1 + (v16 + P[v18]))
if (v20 + 35) > length then return false end
if P[(v20 + 34)] == 3 then return true end
goto L59
end
::L59::
if v19 ~= 1 then goto L49 end
if (v17 + 36) > length then return false end
if P[v18] == 3 then return true end
goto L49
end
::L49::
if v15 ~= 1 then goto L39 end
local v21 = (v13 + 36)
if v21 > length then return false end
local v22 = P[v14]
if v22 == 3 then return true end
if v22 == 1 then goto L77 end
do
if (v13 + 37) > length then return false end
local v23 = (v1 + (v12 + P[v21]))
if (v23 + 36) > length then return false end
if P[(v23 + 35)] == 3 then return true end
goto L77
end
::L77::
if v22 ~= 1 then goto L39 end
if (v13 + 37) > length then return false end
if P[v21] == 3 then return true end
goto L39
end
::L39::
if v11 ~= 1 then goto L29 end
local v24 = (v9 + 36)
if v24 > length then return false end
local v25 = P[v10]
if v25 == 3 then return true end
if v25 == 1 then goto L95 end
do
if (v9 + 37) > length then return false end
local v26 = (v8 + P[v24])
local v27 = (v1 + v26)
local v28 = (v27 + 36)
if v28 > length then return false end
local v29 = P[(v27 + 35)]
if v29 == 3 then return true end
if v29 == 1 then goto L105 end
do
if (v27 + 37) > length then return false end
local v30 = (v1 + (v26 + P[v28]))
if (v30 + 36) > length then return false end
if P[(v30 + 35)] == 3 then return true end
goto L105
end
::L105::
if v29 ~= 1 then goto L95 end
if (v27 + 37) > length then return false end
if P[v28] == 3 then return true end
goto L95
end
::L95::
if v25 ~= 1 then goto L29 end
local v31 = (v9 + 37)
if v31 > length then return false end
local v32 = P[v24]
if v32 == 3 then return true end
if v32 == 1 then goto L123 end
do
if (v9 + 38) > length then return false end
local v33 = (v1 + (v8 + P[v31]))
if (v33 + 37) > length then return false end
if P[(v33 + 36)] == 3 then return true end
goto L123
end
::L123::
if v32 ~= 1 then goto L29 end
if (v9 + 38) > length then return false end
if P[v31] == 3 then return true end
goto L29
end
::L29::
if v7 ~= 1 then goto L19 end
local v34 = (v5 + 36)
if v34 > length then return false end
local v35 = P[v6]
if v35 == 3 then return true end
if v35 == 1 then goto L141 end
do
if (v5 + 37) > length then return false end
local v36 = (v4 + P[v34])
local v37 = (v1 + v36)
local v38 = (v37 + 36)
if v38 > length then return false end
local v39 = P[(v37 + 35)]
if v39 == 3 then return true end
if v39 == 1 then goto L151 end
do
if (v37 + 37) > length then return false end
local v40 = (v36 + P[v38])
local v41 = (v1 + v40)
local v42 = (v41 + 36)
if v42 > length then return false end
local v43 = P[(v41 + 35)]
if v43 == 3 then return true end
if v43 == 1 then goto L161 end
do
if (v41 + 37) > length then return false end
local v44 = (v1 + (v40 + P[v42]))
if (v44 + 36) > length then return false end
if P[(v44 + 35)] == 3 then return true end
goto L161
end
::L161::
if v43 ~= 1 then goto L151 end
if (v41 + 37) > length then return false end
if P[v42] == 3 then return true end
goto L151
end
::L151::
if v39 ~= 1 then goto L141 end
local v45 = (v37 + 37)
if v45 > length then return false end
local v46 = P[v38]
if v46 == 3 then return true end
if v46 == 1 then goto L179 end
do
if (v37 + 38) > length then return false end
local v47 = (v1 + (v36 + P[v45]))
if (v47 + 37) > length then return false end
if P[(v47 + 36)] == 3 then return true end
goto L179
end
::L179::
if v46 ~= 1 then goto L141 end
if (v37 + 38) > length then return false end
if P[v45] == 3 then return true end
goto L141
end
::L141::
if v35 ~= 1 then goto L19 end
local v48 = (v5 + 37)
if v48 > length then return false end
local v49 = P[v34]
if v49 == 3 then return true end
if v49 == 1 then goto L197 end
do
if (v5 + 38) > length then return false end
local v50 = (v4 + P[v48])
local v51 = (v1 + v50)
local v52 = (v51 + 37)
if v52 > length then return false end
local v53 = P[(v51 + 36)]
if v53 == 3 then return true end
if v53 == 1 then goto L207 end
do
if (v51 + 38) > length then return false end
local v54 = (v1 + (v50 + P[v52]))
if (v54 + 37) > length then return false end
if P[(v54 + 36)] == 3 then return true end
goto L207
end
::L207::
if v53 ~= 1 then goto L197 end
if (v51 + 38) > length then return false end
if P[v52] == 3 then return true end
goto L197
end
::L197::
if v49 ~= 1 then goto L19 end
local v55 = (v5 + 38)
if v55 > length then return false end
local v56 = P[v48]
if v56 == 3 then return true end
if v56 == 1 then goto L225 end
do
if (v5 + 39) > length then return false end
local v57 = (v1 + (v4 + P[v55]))
if (v57 + 38) > length then return false end
if P[(v57 + 37)] == 3 then return true end
goto L225
end
::L225::
if v56 ~= 1 then goto L19 end
if (v5 + 39) > length then return false end
if P[v55] == 3 then return true end
goto L19
end
::L19::
if v3 ~= 1 then return false end
local v58 = (v1 + 36)
if v58 > length then return false end
local v59 = P[v2]
if v59 == 3 then return true end
if v59 == 1 then goto L243 end
do
if (v1 + 37) > length then return false end
local v60 = P[v58]
local v61 = (v1 + v60)
local v62 = (v61 + 36)
if v62 > length then return false end
local v63 = P[(v61 + 35)]
if v63 == 3 then return true end
if v63 == 1 then goto L253 end
do
if (v61 + 37) > length then return false end
local v64 = (v60 + P[v62])
local v65 = (v1 + v64)
local v66 = (v65 + 36)
if v66 > length then return false end
local v67 = P[(v65 + 35)]
if v67 == 3 then return true end
if v67 == 1 then goto L263 end
do
if (v65 + 37) > length then return false end
local v68 = (v64 + P[v66])
local v69 = (v1 + v68)
local v70 = (v69 + 36)
if v70 > length then return false end
local v71 = P[(v69 + 35)]
if v71 == 3 then return true end
if v71 == 1 then goto L273 end
do
if (v69 + 37) > length then return false end
local v72 = (v1 + (v68 + P[v70]))
if (v72 + 36) > length then return false end
if P[(v72 + 35)] == 3 then return true end
goto L273
end
::L273::
if v71 ~= 1 then goto L263 end
if (v69 + 37) > length then return false end
if P[v70] == 3 then return true end
goto L263
end
::L263::
if v67 ~= 1 then goto L253 end
local v73 = (v65 + 37)
if v73 > length then return false end
local v74 = P[v66]
if v74 == 3 then return true end
if v74 == 1 then goto L291 end
do
if (v65 + 38) > length then return false end
local v75 = (v1 + (v64 + P[v73]))
if (v75 + 37) > length then return false end
if P[(v75 + 36)] == 3 then return true end
goto L291
end
::L291::
if v74 ~= 1 then goto L253 end
if (v65 + 38) > length then return false end
if P[v73] == 3 then return true end
goto L253
end
::L253::
if v63 ~= 1 then goto L243 end
local v76 = (v61 + 37)
if v76 > length then return false end
local v77 = P[v62]
if v77 == 3 then return true end
if v77 == 1 then goto L309 end
do
if (v61 + 38) > length then return false end
local v78 = (v60 + P[v76])
local v79 = (v1 + v78)
local v80 = (v79 + 37)
if v80 > length then return false end
local v81 = P[(v79 + 36)]
if v81 == 3 then return true end
if v81 == 1 then goto L319 end
do
if (v79 + 38) > length then return false end
local v82 = (v1 + (v78 + P[v80]))
if (v82 + 37) > length then return false end
if P[(v82 + 36)] == 3 then return true end
goto L319
end
::L319::
if v81 ~= 1 then goto L309 end
if (v79 + 38) > length then return false end
if P[v80] == 3 then return true end
goto L309
end
::L309::
if v77 ~= 1 then goto L243 end
local v83 = (v61 + 38)
if v83 > length then return false end
local v84 = P[v76]
if v84 == 3 then return true end
if v84 == 1 then goto L337 end
do
if (v61 + 39) > length then return false end
local v85 = (v1 + (v60 + P[v83]))
if (v85 + 38) > length then return false end
if P[(v85 + 37)] == 3 then return true end
goto L337
end
::L337::
if v84 ~= 1 then goto L243 end
if (v61 + 39) > length then return false end
if P[v83] == 3 then return true end
goto L243
end
::L243::
if v59 ~= 1 then return false end
local v86 = (v1 + 37)
if v86 > length then return false end
local v87 = P[v58]
if v87 == 3 then return true end
if v87 == 1 then goto L355 end
do
if (v1 + 38) > length then return false end
local v88 = P[v86]
local v89 = (v1 + v88)
local v90 = (v89 + 37)
if v90 > length then return false end
local v91 = P[(v89 + 36)]
if v91 == 3 then return true end
if v91 == 1 then goto L365 end
do
if (v89 + 38) > length then return false end
local v92 = (v88 + P[v90])
local v93 = (v1 + v92)
local v94 = (v93 + 37)
if v94 > length then return false end
local v95 = P[(v93 + 36)]
if v95 == 3 then return true end
if v95 == 1 then goto L375 end
do
if (v93 + 38) > length then return false end
local v96 = (v1 + (v92 + P[v94]))
if (v96 + 37) > length then return false end
if P[(v96 + 36)] == 3 then return true end
goto L375
end
::L375::
if v95 ~= 1 then goto L365 end
if (v93 + 38) > length then return false end
if P[v94] == 3 then return true end
goto L365
end
::L365::
if v91 ~= 1 then goto L355 end
local v97 = (v89 + 38)
if v97 > length then return false end
local v98 = P[v90]
if v98 == 3 then return true end
if v98 == 1 then goto L393 end
do
if (v89 + 39) > length then return false end
local v99 = (v1 + (v88 + P[v97]))
if (v99 + 38) > length then return false end
if P[(v99 + 37)] == 3 then return true end
goto L393
end
::L393::
if v98 ~= 1 then goto L355 end
if (v89 + 39) > length then return false end
if P[v97] == 3 then return true end
goto L355
end
::L355::
if v87 ~= 1 then return false end
local v100 = (v1 + 38)
if v100 > length then return false end
local v101 = P[v86]
if v101 == 3 then return true end
if v101 == 1 then goto L411 end
do
if (v1 + 39) > length then return false end
local v102 = P[v100]
local v103 = (v1 + v102)
local v104 = (v103 + 38)
if v104 > length then return false end
local v105 = P[(v103 + 37)]
if v105 == 3 then return true end
if v105 == 1 then goto L421 end
do
if (v103 + 39) > length then return false end
local v106 = (v1 + (v102 + P[v104]))
if (v106 + 38) > length then return false end
if P[(v106 + 37)] == 3 then return true end
goto L421
end
::L421::
if v105 ~= 1 then goto L411 end
if (v103 + 39) > length then return false end
if P[v104] == 3 then return true end
goto L411
end
::L411::
if v101 ~= 1 then return false end
local v107 = (v1 + 39)
if v107 > length then return false end
local v108 = P[v100]
if v108 == 3 then return true end
if v108 == 1 then goto L439 end
do
if (v1 + 40) > length then return false end
local v109 = (v1 + P[v107])
if (v109 + 39) > length then return false end
if P[(v109 + 38)] == 3 then return true end
goto L439
end
::L439::
if v108 ~= 1 then return false end
if (v1 + 40) > length then return false end
return P[v107] == 3
end |
takikawa
added a commit
to takikawa/pflua
that referenced
this issue
Dec 7, 2016
This test exercises spilling for the dynasm backend pretty well and exposed a bug
takikawa
added a commit
that referenced
this issue
Dec 9, 2016
Fix spilling & add a big test from issue #215
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The following pflang is from Juho Snellman's blog post, and looks for the window-scaling option among the first 6 TCP options. I think it miscompiles though, because it looks like the whole ip6 block folds for some reason.
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